Source:  The Soviet Socialist Republic of Iran, 1920-1921: Birth of the Trauma by Cosroe Chaqueri, University of Pittsburgh Press, Pittsburgh and London, 1995.

It has this on Pishevari in the Appendix (p. 470):

Pishevari, Seyyed J'afar Javâdzâdeh (b. 1892)

The third important Communist leader who played a significant role in the SSRI [Soviet Socialist Republic of Iran] was born to a humble family of Khalkhal, Azerbaijan, in 1892. In 1905 he moved to Baku, where he received his revolutionary education, He joined revolutionaries in the Caucasus and collaborated with the 'Adalat [justice] movement. A well-educated man, he soon became an influential journalist in Baku and published in legal as well as illegal newspapers of the region, such as Achiq Souz, Horriyat, Azerbaijan Foqarasi, Kommunist, Yeni Youl, Yeni Fekr, and many others.

Back in Iran, Pishevari initially worked for the ICP in Gilan and became commissar of the interior in its Communist-led government formed at the end of July 1920. After the demise of the Jangali Movement, he was the lead writer of the Communist newspaper Haqiqat [Truth] published in Teheran. In 1921 he represented the ICP at the third Comintern congress and defended the cause of the party's radical wing. He worked among Iranian workers until his arrest as one of those responsible for the great oil workers' strike in Khuzistan in 1929. He was a member of the ICP Central Committee until his arrest in December 1930. Released after the abdication of Reza Shah in 1941, he refused to join the Tudeh party. He founded the newspaper Azhir (Siren) and advocated a radical democratic line.

In 1944 he was elected to the fourteenth Majles, but was rejected by the reactionary-dominated body. Returning to his native province, he established the Democratic party of Azerbaijan, whose main demand was local autonomy from Teheran. After Soviet troops left Iran in 1946 under international pressure, the autonomous government at Tabriz fell instantly. Baqerov, the president of the Azerbaijan SSR, blamed Pishevari for his party's failure to insist on uniting Iranian Azerbaijan and Soviet Azerbaijan. Pishevari stated that his movement failed precisely because Iranians had the impression that the party wanted the province to secede from Iran and join the ASSR. After a bitter exchange, Pishevari was killed in a mysterious automobile accident, widely interpreted as arranged by Baqerov. ( Footnote 45)

Footnote 45 on p. 611: Mir Ja'far Pishevari (Javâdzâdeh Khalkhali), Sa'chilmish Asarlari (Baku, 1965); J. Pishevari, Târikhcheh-yi Hezb-i 'Adalat (Teheran, 1980); and Yâd-dâshthâ-yi Zendan (Tehran, n.d.; prt. Los Angeles, 1988); N. Jahânshâhlou-Afshâr, Sargozasht, Mâ va Bigânegân, vol. 2 (Berlin, 1988). In spite of denials, one of his erstwhile lieutenants in Baku told me [Chaqueri] in September 1992 that Pishevari's death in spring 1947 was ordered by Soviet leaders.